Polarity reversing switch for electron tube



March 12, 196.8

POLARITY REVERSING SWITCH FOR ELECTRON TUBE Filed 001,. 7, 1955 P. F2. FRUZZETTH March 12, 1968 P. R. FRUZZETTH POLARITY REVERSING SWITCH FOR ELECTRON TUBE Filed Oct. 7, 1965 2 Sheets-shewl 2 United States Patent Otice 3,373,289 Patented Mar. 12, 1968 3,373,289 POLARITY REVERSlNG SWITCH FOR ELECTRON TUBE Paul R. Fruzzctti, Brockton, Mass., assignor to National Research Corporation, Cambridge, Mass., a corporation of Massachusetts Filed Oct. 7, 1965, Ser. No. 493,719 1 Claim. (Cl. 307-113) ABSTRACT F THE DSCLOSURE Polarity reversing electrical switch for use with high voltage discharge tube having two modes of operation at opposite pola-titles. The switch has a switching member which is movable in rotational and translational senses and is provided with a chassis plate having spaced guide apertures for the movable member.

The present invention relates to high voltage electrical circuit components and particularly to a polarity reversing switch.

It is the principal object of the invention to provide a polarity reversing switch which switches a pair of output terminals between positive and negative high voltages with a built-in delay which allows stored charge in the circuit to dissipate during switching.

t is a further object of the invention to provide a polarity reversing switch which can be mounted on an instrument chassis panel and guide the operator in making the switch connections.

lt is a further object of the invention to provide a polarity reversing switch with `auxiliary microswitches mounted thereon for circuit on-oft control in addition to polarity reversing control.

It is a further object of the invention to provide a polarity reversing switch which is useful for electrical power supply circuits of tubes which operate in glow discharge condition under one mode of operation and under controlled thermionic emission in another mode of operation, the two modes corresponding to the two settings of the polarity reversing switch.

Other objects, features and advantages of the invention will, in part, be obvious and will, in part, appear hereinafter from and in the following description, read in conjunction with the accompanying drawings wherein: FIG. 1 is a schematic diagram of a discharge tube and its power supply circuit, including the new polarity reversing switch;

FIG. 2 is a sectional side View of the polarity reversing switch;

FIG. 2A is an end view of the switch from in front of the circuit chassis plate;'and

FIG. 2B is an end view of the plug board of the switch.

FIG. 3 is an end View of the switch from behind the chassis plate.

Referring now to FIG. l, there is shown the tube and circuit in which the polarity reversing switch of the invention is utilized. The tube is an orbiting electron vacuum pump with a thermionic filament 12, a central anode rod 14 supporting a slug 16 of getter material and a grounded metal body 16. The pump is used for evacuating a vacuum system which includes roughing pump and the usual vacuum system accessories (not shown). The pump is provided with power from conventional industrial or laboratory alternating current power supply through main power switches S and 52 and a main autotransformer 34. Connected to the autotransformer are a rectifier for providing a high voltage bias on the pump it! and a second autotransformer 64 for providing heating power to the pump filament 18 via transformer 50.

The rectifier 30 is connected to the pump through a polarity reversing switch 4t) and a 20K load resistor 42. A 10M bleed resistor' 44 and a 0.1 microfarad capacitor 48 are provided in parallel with the load resistor. The polarity reversing switch has output terminals T1 and T2 and input terminals T3 and T4. Terminal T3 is connected to the positive output, and terminal T4 to the negative output, of the rectifier 30. The polarity reversing switch also controls the switches 52 and 51.

The filament heating circuit comprises a manual independent on-off switch 53 in addition to the above-mentioned switch 51 which is operated in conjunction with the polarity reversing switch 40. A variable resistor 56 connected between the filament heating circuit and ground provides a positive bias on the filament 18. Topped off from the filament heating circuit are a transformer 62 and a diode 6d, with a capacitor 66 for providing a reference voltage to a 2.5K current comparison resistor 68. A voltage drop is developed across resistor 68 in response to total current within pump 16 and this voltage bucks the reference voltage to provide a net voltage which regulates filament emission via a saturable reactor which comprises direct current windings 70A and alternating current windings 70B.

- The operation of the pump 10 is as follows, starting from atmospheric pressure in the system 2t) and power of (switch S open). The operator evacuates the system 20 and pump 10 to a rough vacuum on the order of l0 microns using a roughing pump (not shown). Then the operator sets the polarity reversing switch to a START position wherein high negative voltage will be applied to output terminal T1. Then the operator closes the main power switch S. Operation of the polarity reversing switch 40 has already closed switch 52. The operator adjusts the autotransformer to start a glow discharge in the pump 10. The glow discharge cleans the pump and reduces pressure to the point where the pump can operate in its normal mode. The operator then opens the switch S and turns the polarity reversing switch to its RUN position. Then the operator closes switches S and S3. The above operation of switch 40 to its RUN position closes switch 51. High positive voltage is now applied to terminal T1 and thus to anode 12. Heating current is applied to filament 18 for thermionic emission of electrons. The electrons orbit around anode 12 and ionize gas molecules and strike the cylinder 14 to evaporate getter material. Manual regulation of bias and emission during running is provided through autotransformers 34 and 64 and resistor 56 and automatic regulation of emission current is provided through saturable reactor windings 70A and 70B.

The above description of pump operation demonstrates the basic functions assigned to the polarity reversing switch 40. The switch must reliably switch T1 from positive to negative high voltage (about 5 to 15 kilovolts). lf the operator forgets to open switch S to cut ott power before operating switch 40, the switch 40 must accomplish the same function by opening switch 52 whenever switch 40 is operated from START to RUN or from RUN to START, or in between. Otherwise dangerous arcing would occur at switch terminals. If the operator forgets to open switch 53 after a RUN cycle, switch 40 must accomplish the same function by opening switch 51. Otherwise, the filament 18 will be heated at undesired times (eg. when the pump is not under vacuum, leading to breakage or contamination of the filament).

In addition, there is a requirement that the switch must delay from breaking one contact to making another (on the order of one second). This allows the capacitor 4S to dissipate its stored charge through bleed resistor 44.

Referring now to FIGS. 2-3, there is shown the construction of my improved polarity reversing switch which performs these diverse functions.

The elements of the switch are:

(a) a fixed member F comprising a jack board 101 mounting four terminals 121, 122, 123, 124 and four corresponding jacks J and having an aperture 110 and a switch bracket 104.

(b) a moveable member M comprising a plug board 102 mounting four terminals 131, 132, 133, 134 and four corresponding banana plugs P and a hex bolt extension 105 and a guide rod 106 and a nylon screw extension 107.

(c) a chassis plate 140 with a central aperture 141 and auxiliary apertures 142, 143.

(d) a knob 103 mounted on said guide having a stop rod extension 103A.

(e) the above-described switch 52 mounted on said switch bracket 104.

(f) the above-described switch 51 mounted on said switch bracket 104.

(g) a spring 109 loosely riding on said guide rod, and

(h) three spaced ceramic standoffs 10S mounting the fixed member F from the chassis plate 140.

FIGURE 2 indicates the usage herein of forward and rearward with respect to chassis plate 140.

In order to switch between RUN and START, the operator pulls knob 103 forward so that stop rod 103A clears aperture 142 so that the banana plugs P clear the jacks J thus breaking the power supply circuit for biasing the cathode and anode of pump 10. Then the operator rotates knob 103 to the other position. During the rotation, spring 109 is compressed between chassis plate 140 and plug board 102, thus forcing rod 103A against the chassis plate. If the operator lets go of knob 103, it will stay in position. The operator completes a 90 rotation of the switch to START POSITION and moves the memrod 106 and ber M forward with the assistance of spring 109 to insert jacks J into plugs P in the new arrangement. Rod 103A slides through aperture 143 in this forward movement.

Firm seating of the moveable member is required to close the main power switch 52 which is directly in the translation path of member M (extension 10S thereof) at the end of the rearward stroke. Of course, extension 109 is 90 displaced from switch 51 in the START position. Switch 51 therefore remains open. In the START position extension 109 passes through another aperture (not shown) in the chassis plate 101.

The sequence of events is essentially the same in going from START back to the RUN position shown in the drawings.

In either sequence, the forward-rotate-rearward movements of the moveable member M provide the necessary time delay to allow dissipation of stored charge in the power supply circuit.

The switch allows a considerable versatility to the circuit designer. A typical assignment of roles is shown in FIG. 3 wherein:

Terminal 121 is T1 of the circuit (FIG. 1) Terminal 122 is T2 of the circuit.

Terminal 12.3 is T3 of the circuit. Terminal 124 is T4 of the circuit.

The plug board FIG. 2-B has a jumper wire W between terminals 131 and 134 and another jumper wire W between 132 and 133. However, it will be apparent that many other wiring arrangements could be made utilizing the polarity reversing switch to advantage.

What is claimed is:

1. In a high voltage discharge tube wherein the tube has a first mode of operation consisting of a glow discharge and a second mode of operation wherein gas molecules in the tube are ionized by thermionic electrons, and a power supply therefor, the tube comprising a grounded electrode and high voltage electrode and at least one thermionic filament, the power supply comprising a main power input line connected to a rectifier, positive and negative output terminals of said rectifier connected to input terminals of a polarity reversing switch, said switch having first and second output terminals connected to said grounded and high voltage electrodes respectively, an auxiliary power input line connected to said filament, an improved polarity reversing switch comprising (a) a first and fixed member supporting a first set of four spaced connectors in a circular array with an aperture at the center of the array, said input and output terminals extending from said connectors of the first set,

(b) a second member constructed and arranged for translation and rotational movements, supporting a second set of four spaced connectors in a circular array and means mounted on said second member for tying the connectors of each second set together in twos, a guide rod extending from said second member at the center of said circular array and extending outwadly on both sides of said second member,

(c) a chassis plate with an aperture therein, the first said member being mounted on and behind the chassis plate by standofis and the said apertures of the chassis plate and first member bein-g coaxial, the said second member being located and arranged with the said guide rod extending through said apertures,

(d) a knob mounted on the guide rod in front of the chassis plate, a stop rod mounted from said knob and extending to the chassis plate, a pair of spaced apertures on said `chassis plate for accommodating the stop rod at the limits of rotational movement of the second member corresponding to the switching positions providing said first and second modes of operation after rod.

(e) a first power cut-ofi switch mounted on said first member and in the translation path of said first member in all rotary positions thereof,

(f) an auxiliary power cut-ofi switch mounted on said first member and in the translation path of the second member in one rotary position of the second member, and

(g) a spring mounted on the second member to restrain movement of said second member toward said chassis plate.

References Cited UNITED STATES PATENTS 2,201,875 5/ 1940 Zelt 20G-51.04 2,986,612 5/1961 Healy 20o-51.09

DAVID I GALVIN, Primary Examiner. 

